Screwdriver blade



March 1965 P. LAUNAY 3,175,593

.SCREWDRIVER BLADE Filed March 27, 1962 3 Sheets-Sheet 1 March 30, 1965P. LAUNAY 3,175,593

' SCREWDRIVER BLADE Filed March 2'7, 1962 3 Sheets-Sheet 2 United StatesPatent 4 Claims. (cl. 145-50 The present invention relates to screws andscrewdrivers.

A characteristic feature of the invention resides in providing the headof the screw with a slot of substantially diamond-shaped cross section,with the side walls of this slot flaring outwardly at a small angle, thebottom of said slot being flat with the exception of its central part,where it is provided with a conical guiding axial hole the apex angle ofwhich is at least approximately equal to said small angle, such a slotforming a female part adapted to cooperate with a male part consistingof a screwdriver blade of substantially diamond-shaped cross section andtapering at said small angle toward its end, said blade end beingprovided in its central part with a frusto-conical axial projectionadapted to fit in said conical hole of the slot.

Such an arrangement makes it possible, on the one hand, to facilitatethe formation of a slot in the screw head by stamping by means of apunch of the same shape as the above mentioned screwdriver and, on theother hand, to facilitate the holding of the screw by the end of thescrewdriver, as will be hereinafter explained.

A preferred embodiment of my invention will be hereinafter describedwith reference to the appended drawings given merely by way of exampleand in which:

FIG. 1 is a sectional view on the line I-I of FIG. 3;

FIG. 2 is a sectional view on the line II-II of FIG. 3;

FIG. 3 is a plan view of the same screw;

FIG. 4 is a side View of a blank to be used for making a punch forobtaining, by stamping, the slot in the screw head;

FIG. 5 is an end view of the blank of FIG. 4;

FIG. 6 is a side view of the punch obtained from the blank of FIGS. 4and 5;

FIG. 7 is an end view, corresponding to FIG. 5, showing the forming ofthe punch;

FIG. 8 shows, on an enlarged scale, the punch of FIG. 7;

FIG. 9 is a view similar to FIG. 8 but relating to a modification;

FIG. 10 is a perspective view cording to this invention; and

FIGS. 11 to 13 inclusive show, in three diiferent positions, theengagement of the screwdriver into the slot of a screw according to thisinvention.

The screw of FIGS. 1 to 3 comprises a shank 1 and a head 2 provided witha slot 3.

This slot has, in plan view and also in horizontal cross section, adiamond shape outline, preferably of a length smaller than the diameterof the screw head, as shown.

This slot has outwardly flaring side walls, with a small angle ofinclination.

The bottom of slot 3 is flat, with the exception of its central part,which is provided with a blind hole 4, this hole being of conical shape,with an apex angle preferably equal to the above mentioned small angleof inclination of the side walls of the diamond-shaped slot, thediameter of this hole 4 being such that it is substantially inscribed inthe diamond-shaped bottom of the slot.

The first advantage of this arrangement is that it permits of easilyobtaining the slot by stamping by means of a punch of correspondingshape. The flaring disposition of the walls of the slot facilitatesstamping and the of a screwdriver ac- 3,175,593 Patented Mar. 30, 1965"ice diamond shape ensures a great resistance of the punch and also abetter distribution of the metal in the screw head during stamping. Inparticular, this stamping is advantageously performed on a screw blankthe head of which has in plan view a slightly oval shape, the punchbeing disposed with the major axis of its diamondshaped section incoincidence with the major axis of the oval. The distribution of themetal after stamping will be such as to transform the oval into acircle.

Secondly, this arrangement, in combination with the use of a screwdriverof a shape corresponding to that of the slot, will permit, when it isdesired to put a screw into a desired place, of wedging the end of thescrewdriver blade into the slot, thus ensuring a temporary holding ofthe screw by the screwdriver.

Thirdly, the fact that the screwdriver is provided with a conicalprojection adapted to fit into the central hole of the screw facilitatesthe positioning of the screwdriver with respect to the screw as it willbe hereinafter explained with reference to FIGS. 11 to 13.

Slot 3 is of a length smaller than the diameter of the screw head. Itsopposed side walls 14 and end walls 15 are slightly inclined withrespect to each other at an angle 2A (FIGS. 1 and 2) equal to 8 butwhich may range from 6 to 10.

Similarly, the guiding hole 4 has an apex angle at least approximatelyequal to this value.

The horizontal cross sections are diamond-shaped, as shown by FIG. 3,angle B having, for instance, a value of 20.

The punch to be used for obtaining such a slot 3 in the head 2 of thescrew by stamping is advantageously obtained (FIGS. 4 to 8) from a blank16 including a cylindrical portion 17 and a conical projection 18(intended to form the guiding hole 4).

The side faces 19, 19 of the punch are obtained by milling of part 17 bymeans of a milling tool 21 as shown by FIG. 7.

These faces 19, 19 make an angle of with each other.

Faces 19, 19 may either be tangent to the conical surface of projection18, as shown by FIG. 9, or intersect this conical surface as shown bythe other figures. In this last case the intersection with conicalprojection 18 produces two flat surfaces 19 19 respectively in line withfaces 19 and which intersect each other along a generatrix of conicalsurface 18 (FIG. 6).

Two small fiat surfaces 22 formed in hole 4 (FIGS. 1 and 3) correspondto said surfaces 19 19 Of course, when the milling operation illustratedby FIG. 7 is being performed, the axis of milling tool 21 is suitablyinclined to obtain angle B and angle A.

The screwdriver 30 (FIG. 10) to be used with screws made as abovedescribed has a shape analogous to that of the punch to be used formaking the slots in the screw heads. The blade of this screwdrivercomprises two faces 19 making an angle almost equal to with each otherand tapering toward the blade end, these faces 19 extending to form thesmall faces 19 and 19 on opposite sides of conical projection 18 of theblade.

The end of this projection 18 is given the shape of a convex portion ofa sphere and the bottom 41 of hole 4 is of corresponding shape.

Screws according to the present invention can be manufactured in greatquantities by stamping owing to the inclination of the slot side wallsand also to the great strength of the corresponding punch which furtherproduces a correct distribution of the metal of the screw head when itis deformed.

Furthermore the end portion of the screwdriver blade is of greatrigidity owing to its diamond-shaped cross section.

The screw can be held at the end of the screwdriver screw head slot isvery easy owing to the guiding of projection 18 in hole 4, asillustrated by FIGS. 11 to 13.

The operator can easily handle the screwdriver to introduce projection18 therein into slot 3. This is made still easier by the convex roundedshape 40 of the end of projection18. This operation is illustrated byFIG. 11 where the projection 18 is inserted at one end of slot 3.

If, now, the screwdriver is moved, projection 18 is guided in slot 3 andnecessarily drops into hole 4 where it fits exactly (position of FIG.12).

It remains only to pivot the screwdriver about its axis,

for instance in the direction of arrow F (FIG. 12) and finally the endof the blade engages slot 3 where it fits exactly as shown by FIG. 13.

If the screwdriver is pressed 'with some force, the end of its bladewedges slightly in slot 3 so that the screw is held by the screwdriver.v

The respective depths h and k (FIG. 1) of slot 3 and hole 4 have beensupposed in the example shown to be of the same order of magnitude, butthey might be different. In particular the depth k of hole 4 (and thecorresponding length of projection 18) might be greater than h withrespect to said axis as the generatrices of the surface of saidfrusto-conical axial projection, said two planes intersecting saidfrusto-conical surface.

. other along a generatrix of the frusto-conical surface of Furthermore,in all cases, when the screwdriver is env gaged in the screw head slotso as to fit therein there is a very small clearance between the bottomof the slot and that ofthe hole on the one hand and the end 40 ofprojection 18 and the edge of the screwdriver blade on the other hand,so as to permit the wedging effect above referred to.

As a matter of fact, the punch for obtaining the slot in the screw headand the screwdriver will be made of the same dimensions and theretraction of the metal of the screw after heating due to the stampingoperation will somewhat reduce the dimensions of the recesses formed inthe screw head.

Of course, the shape of the screw head is not at all limited to thecountersunk shape illustrated by the drawmg.

In a general. manner, while I have, in the above description, disclosedwhat I deem to be practical and efiicient embodiment of my invention, itshould be well understood that I do not wish to be limited thereto asthere rnight be changes made in the arrangement, disposition and form ofthe parts without departing from the principle of the present inventionas comprehended within the scope of the accompanying claims.

What I claim is: V

l. A screwdriver comprising a blade having an axis of symmetry in itslongitudinal direction, said blade being of substantially diamond-shapedcross section in planes perpendicular to said axis, said blade havingopposed side walls tapering at an acute angle toward an end thereof,said blade end including a centrally located frusto-conical axialprojection the apex angle of which is at least approximately equal tothe acute angle of taper between the opposed side walls, each of saidside walls comprising two flat surfaces located in respective planesintersecting each other along a straight line having the sameinclination said axial projection, said two planes intersecting saidfrusto-conical surface. 7

3. As a new article of manufacture, a blade for a screwdriver to be usedwith a screw having a head wherein is a slot having a diamond-shapedcross section and a centrally located conical hole in the slot andwherein the slot and hole are of a corresponding taper; said blade beingof diamond-shaped cross section and tapering toward an end thereof, saidend having a centrally located conical projection of a tapercorresponding to that of said hole but with a range ofdiameters/relative to that of said hole adapted to prevent theprojection from being inserted fully into the hole and also the bladefrom seating fully in the slot, the walls of the blade defining thediamond-shaped cross section intersecting along a line having the sameinclination with respect to the blade longitudinal axis as thegeneratrices of the conical projection.

4. As a new article of manufacture, a blade for a screwdriver to be usedwith a screw having a head wherein is a slot having a diamond-shapedcross section and a centrally located conical hole in the slot andwherein the slot and hole are of a corresponding jtaperi said bladebeing of diamond-shaped cross section and tapering toward an endthereof, said end having a centrally located conical projection of ataper corresponding to that of said hole but with a range of diametersrelative to that of said hole adapted to prevent the projection frombeing inserted fully into the hole and also the'blade from seating fullyinthe slot, the walls of the blade defining the diamond-shaped crosssection intersecting along a generatrix of the conical projection.

References Cited the file of this patent UNITED STATES PATENTS 52,631Weaver Feb. 13, 1866 1,797,390 Wood Mar. 24, 1931 2,058,197 West Oct.20, 1936 2,140,449 B1'0WI1 l- 'a Dec; 13,1938 2,141,072 Velepec Dec. 20,1938- 2,193,477 De Vellier Mar. 12, 1940 2,238,960 Wilcox Apr. 22, 19412,323,018 De Vell-ier June 29, 1943 2,458,391 Lavietes Jan. 4, 19492,745,120 Vaughn u May 15, 1956 FOREIGN PATENTS 192,195 Switzerland Oct.1, 1937 r l l

1. A SCREWDRIVER COMPRISING A BLADE HAVING AN AXIAL OF SYMMETRY IN ITSLONGITUDINAL DIRECTION, SAID BLADE BEING OF SUBSTANTIALLY DIAMOND-SHAPEDCROSS SECTION IN PLANES PERPENDICULAR TO SAID AXIS, SAID BLADE HAVINGOPPOSED SIDE WALLS TAPERING AT AN ACUTE ANGLE TOWARD AN END THEREOF,SAID BLADE END INCLUDING A CENTRAL LOCATED FRUSTO-CONICAL AXIALPROJECTION THE APEX ANGLE OF TAPER BETWEEN TWO PROXIMATELY EQUAL TO THEACUTE ANGLE OF TAPER BETWEEN THE OPPOSED SIDE WALLS, EACH OF SAID SIDEWALLS COMPRISING TWO FLAT SURFACES LOCATED IN RESPECTIVE PLANESINTERSECTING EACH OTHER ALONG A STRAIGHT LINE HAVING THE SAMEINCLINATION WITH RESPECT TO SAID AXIS AS THE GENERATRICES OF THE SURFACEOF SAID FRUCTO-CONICAL AXIAL PROJECTION, SAID TWO PLANES INTERSECTINGSAID FRUSTO-CONICAL SURFACE.